Wireless signal loss detection

ABSTRACT

An apparatus included a receiver for receiving an audio file signal, a decoder for demodulating the audio file signal; and a processor for polling the decoder for a loss of a phase lock in the demodulating of the audio file signal. The processor resets and reinitializes the decoder in response to the loss in the phase lock loop. The receiver includes 90 MHz radio frequency reception circuit. The decoder comprises an eight-to-four modulation EFM decoder. In the preferred embodiment, the decoder outputs a digital audio stream that conforms to a known I2S audio stream format.

This application claims the benefit, under 35 U.S.C. §365 ofInternational Application PCT/US03/17369, filed Jun. 3, 2003, which waspublished in accordance with PCT Article 21(2) on Dec. 11, 2003 inEnglish and which claims the benefit of U.S. provisional patentapplication No. 60/385,485, filed Jun. 4, 2002.

FIELD OF THE INVENTION

The present invention relates generally to wireless communications, andmore particularly to wireless signal loss detection.

DESCRIPTION OF THE RELATED ART

Many consumers want to enjoy a vast collection of digital audio filesstored on their PC by playing those audio files on an audio system.Users have already been transferring audio files from CD storage ontotheir personal computers. Playing audio files directly from an Internetweb site through a personal computer to a home audio system permitsusing the computer's processing and storage capacities to increase playlists, as well as organize a library of digital music files using ID3tag song data to display artist, album, song title and genre. Wirelesstransmission and reception between a personal computer and the audiosystem would permit a higher quality listening experience for a user

Wireless transmitter and receiver techniques must be able to sendCD-quality digital audio from the personal computer to the audio system.Active users of jukebox-managed personal computer content and Internetaudio listeners seeking alternatives for listening to digital qualitymusic files require a convenient connection between their personalcomputer and audio system. Continuous transmission and reception betweenthe audio file source and the audio system is required for full userexperience in listening to digital quality music files available from apersonal computer or a network site.

Wireless transmission techniques applied to audio files transmitted to awireless receiver can cease its decoding after long periods oftransmission idleness from the audio file transmitter source. A phaselock loop in the decoding by the receiver can unlock. Loss of the phaselock loop by the receiver would require the user to manuallyre-establish a phase lock loop in the decoding of audio filetransmissions from the transmitter. Accordingly there is a need fordetecting signal loss between the receiver and the signal transmitterand automatically resetting a signal phase lock to maintain nearseamless playing of audio files received over a wireless communicationslink.

SUMMARY OF THE INVENTION

The present apparatus includes a receiver for receiving an audio filesignal, a decoder for demodulating the audio file signal, and aprocessor for polling the decoder for a loss of a phase lock in thedemodulating of the audio file signal. The processor resets andreinitializes the decoder in response to the loss in the phase lockloop. The receiver includes 900 MHz radio frequency reception circuitry.The decoder comprises an eight-to-fourteen modulation EFM decoder. In apreferred embodiment, the decoder outputs a digital audio stream thatconforms to a known I2S audio stream format.

The present computer readable medium contains software instructionsthat, when executed by a processor, perform the steps of receiving amodulated audio file signal, demodulating the modulated audio filesignal, polling the demodulating for a loss in a phase lock in thedemodulating, and resetting and reinitializing the demodulating in replyto the loss in the phase lock. The demodulating is preferably ademodulation of an eight-to-fourteen EFM bit digital encodingsynchronized to a 900 MHz range carrier frequency modulated by thedigital encoding

A method for detecting a signal loss in a wireless audio file signaltransmission includes the steps of receiving an audio file signal,decoding the audio file signal, and polling the decoder for a loss of aphase lock in the decoding of the audio file signal. In response to theloss in the phase lock in the decoding the decoder is reset andreinitialized. The step of receiving, preferably, is synchronized to a900 MHz range carrier frequency modulated by the audio file signal. Thestep of decoding includes an eight-to-fourteen bit modulation EFMdecoding.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be obtainedfrom consideration of the following description in conjunction with thedrawings, in which:

FIG. 1 depicts an exemplary communications environment including anInternet network, a computer, a wireless transmitter, a wirelessreceiver, and an audio system.

FIG. 2 is a block diagram of an exemplary wireless receiver forimplementing the invention; and

FIG. 3 depicts a wireless phase locked loop unlocked condition andrecovery flow chart suitable for use in the receiver of FIG. 2;

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

FIG. 1 depicts an exemplary communications environment 10 including anexemplary network 12, such as the Internet, a personal computer 11 withwireless transmitter 13, and a wireless receiver 14. The wirelesstransmitter 13 transfers audio files on the computer 11 to the wirelessreceiver 14 over wireless medium 15. The wireless receiver then sendsthe analog stereo signal to the audio system 16. The audio files can beany one of various file types, such as mp3, files stored for retentionduring shutoff of the computer or stored temporarily when the computerserves as a conduit for transmission of audio files from across thenetwork to the wireless receiver 14. The transmitter 13 can be anintegral component of the computer's architecture or an add-on devicecommunicating with the computer through a port connection, such as auniversal serial bus connection USB. The exemplary computer 11, shown asa laptop computer, can be a desktop computer system or a processor baseddevice capable of relaying transfer of audio files from across a networkto the wireless receiver 14.

FIG. 2 is a block diagram of an exemplary wireless receiver. An incomingmodulated or encoded analog signal received at an antenna 25 is receivedinto the reception circuitry board 23 containing a frequency synthesizerfor synchronizing the receiver to an exemplary transmitter carrierfrequency in the range of 900 MHz. The encoded signal is decoded by aneight-to-fourteen modulation decoder 22. Eight-to-fourteen EFM encodingis a known encoding technique for compact disk CD encoding. A digitalaudio stream I2S from the decoder 22 is changed by the stereodigital-to-analog converter DAC 21 into an analog stereo input signal toan audio system. Communications protocols between the decoder 22 andprocessor 24 preferably conform to known I2C bus protocols. Theprocessor is preferably a microprocessor tied over a microwire bus tothe reception circuitry 23. The processor controls the frequencysynthesizer for synchronizing the receiver to the radio carrierfrequency of the audio file signal source transmitter. Themicroprocessor continually queries the EFM decoder and determineswhether the decoder's EFM PLL is locked or unlocked. If the EFM PLL isunlocked, then the microprocessor will perform an EFM decoder soft resetand re-initialization. The processor 24 else-carries out the inventivewireless audio file signal loss detection and resetting andinitialization of the decoder 22 when a loss of the wireless audio filesignal is detected.

FIG. 3 is a flow chart for detecting a wireless phase lock loop PLLunlocked condition and recovery flow chart for use in the receiver ofFIG. 2. The processor 24 continually polls the decoder 32 to determineif a phase lock loop in the demodulation of the incoming audio filesignal has been lost 33. If the decoder's phase lock loop PLL hasunlocked the processor undertakes a software reset of the decoder andreinitializes a phase lock loop condition in the decoding of the audiofile signal received at the antenna 25. If the decoder's phase lock loopPLL remains locked, the processor 24 continues to poll the decoder foran unlocked condition in the phase lock loop. The automatic EFM PLLunlocked condition detection and recovery allows for no user awarenessor intervention requirement.

Although various embodiments which incorporate the teachings of thepresent invention have been shown and described in detail herein, thoseskilled in the art can readily devise many other varied embodiments thatwill still incorporate these teachings. The present invention has beendescribed within the context of an audio system receiving transmissionof audio files from a personal computer. It will be appreciated by thoseskilled in the art that the teachings of the present invention directedto wireless signal loss detection recovery may be practiced where thewireless signal is transmitting audio files stored on the computer oraudio files downloaded from across the network onto the computer forstreaming transfer to the audio system. The audio system can be equippedwith an analog stereo input jack, e.g. a home stereo with a “LINE” or“AUX” jack, for receiving the stereo audio signal.

1. Apparatus comprising: a receiver for receiving an audio file signal;a decoder for demodulating said audio file signal; and a processorconfigured to poll said decoder for a loss of a phase lock loop in saiddemodulating of said audio file signal to detect audio file signal lossbetween the receiver and a transmitter, wherein the processor is furtherconfigured to, in response to said loss in said phase lock loop,automatically and repeatedly reset and reinitialize said decoderthroughout a period of signal transmission idleness at a transmittersource until a transmission signal is received and a phase lock loop isestablished.
 2. The apparatus of claim 1, wherein said processor resetsand reinitializes said decoder in response to said loss in said phaselock loop such that seamless playing of audio files is maintained. 3.The apparatus of claim 1, wherein said receiver comprises 900 MHz radiofrequency reception circuitry.
 4. The apparatus of claim 1, wherein saiddecoder comprises an eight-to-fourteen modulation EFM decoder.
 5. Theapparatus of claim 1, wherein said decoder outputs a digital audiostream.
 6. The apparatus of claim 5, wherein said digital audio streamconforms to an I2S audio stream.
 7. A non-transitory computer readablemedium having software instructions recorded thereon, wherein thesoftware instructions, when executed by a processor, perform the stepsof: receiving a modulated audio file signal; demodulating said modulatedaudio file signal; polling said demodulating for a loss in a phase lockloop in said demodulating to detect audio file signal loss between areceiver and a transmitter; and in response to said loss in said phaselock loop, automatically and repeatedly resetting and reinitializingsaid demodulating throughout a period of signal transmission idleness ata transmitter source until a transmission signal is received and a phaselock loop is established such that seamless playing of audio files ismaintained.
 8. The computer readable medium according to claim 7,wherein said demodulating is a digital eight-to-fourteen modulationdigital decoding.
 9. The computer readable medium according to claim 7,wherein said receiving is synchronized to a 900 MHz range carrierfrequency modulated by said audio file signal.
 10. The computer readablemedium according to claim 7, wherein said demodulating outputs a digitalaudio stream.
 11. The computer readable medium according to claim 7,wherein said polling is carried out by a processor.
 12. A method fordetecting a signal loss in a wireless audio file signal transmission,said method comprising the steps of: receiving an audio file signal;decoding said audio file signal; polling said decoding for a loss of aphase lock loop in said decoding of said audio file signal to detectaudio file signal loss between a receiver and a transmitter; and inresponse to said loss in said phase lock loop, automatically andrepeatedly resetting and reinitializing said decoding throughout aperiod of signal transmission idleness at a transmitter source until atransmission signal is received and a phase lock loop is established.13. The method of claim 12, further comprising the step of resetting andreinitializing said decoding in response to said loss in said phase lockloop in said decoding such that seamless playing of audio files ismaintained.
 14. The method of claim 12, wherein said step of receivingcomprises 900 MHz range carrier frequency synchronizing.
 15. The methodof claim 12, wherein said step of decoding comprises aneight-to-fourteen bit modulation EFM decoding.
 16. The method of claim12, wherein said step of decoding outputs a digital audio stream. 17.The method of claim 16, wherein said digital audio stream conforms to anUS audio stream.